1. Field of the Invention
The invention relates to monitoring systems, and more specifically to networks for remotely monitoring the condition of devices such as those employed in heating, ventilating, and cooling (HVAC) systems.
2. Description of the Related Art
It is desirable to be able to monitor remotely equipment that may require periodic preventive maintenance and/or that may require rapid response time should a catastrophic failure occur. For example, the components of a building's HVAC system must be monitored or checked frequently. Preventive maintenance must be performed on a constant basis, particularly with larger systems. Fault or failure conditions may vary in degrees of severity, however the contractor responsible for maintaining the HVAC equipment should be made aware of each failure in due course. Since a contractor, in all likelihood, is responsible for the care and maintenance of the installations of multiple clients, and since fault conditions may occur at any time of day or night, it is not practical for a contractor to remain on-site all the time. Remote detection at a central location (for example, the contractor's office) of fault conditions is desirable and often crucial. It is also desirable to know the approximate failure rate or frequency of failure of each piece of equipment. One can make installation recommendations as to which model or brand of equipment is best suited for a particular site, and one can anticipate the failure of an already-installed piece of equipment and specific components therein based on how long it is running.
Some remote monitoring devices have been developed. U.S. Pat. No. 5,629,687 to Sutton et al. describes a universal interface for remotely-monitored security or alarm systems. In Sutton et al., a local control unit at a monitored site can, under an event condition, initiate a telephone call to a central control unit to alert a human operator of an event such as an intrusion, fire, or other emergency at the site. The local control unit, via the telephone link, sends a serial number indicative of the specific site and emergency to the monitoring center computer. The monitoring center computer receives the serial number and alerts a human operator as to the emergency. The human operator can then act accordingly, e.g., establish one- or two-way communication with the local site.
U.S. Pat. No. 5,748,104 to Argyroudis et al. describes a wireless remote telemetry system which provides real-time reading and remote control of devices such as electricity meters. A home base unit communicates with remote metering units via cellular telephone lines. The home base unit also communicates with a central controller operated by the electric utility. When the utility determines that there is too much load on the power grid, for example, the central controller can send messages to an appliance to turn off. A customer could also remotely activate or deactivate an appliance via a cellular phone through the home base unit.
U.S. Pat. No. 5,061,916 to French et al. describes a system for remotely reporting, in graphical format, alarms or other conditions in a building's automation system. Sensors in a building are hooked up via a telephone line to control module which is, in turn, hooked Up to a central controller. When a sensor detects a fault condition, graphical information is compiled at the central controller and transmitted to one or more remote facsimile machines.
All of the above systems and the prior art are limited in scope because they do not allow for sufficient flexibility in routing fault messages to a variety of different potential recipients of such messages via a variety of different media, depending on the urgency or nature of the fault. Also, the above systems and the prior art do not enable customers and contractors to enter or modify such information easily. As an example, a customer that has an HVAC system with a monitoring network may want to send certain non-emergency condition notifications (e.g., filter needs cleaning) to certain individuals (e.g., contractor/maintenance personnel) via a certain medium (e.g., e-mail) and emergency condition notifications (e.g., low or high refrigerant pressure) to other individuals (building owner, contractor, etc.) via other means (e.g., via beeper or other personal communication device). Such a list of who to contact via what means depending on which fault has occurred may be referred to as a "message profile". The conventional device/contractor interface requires a dedicated land line at both the HVAC device and the contractor; that is, the HVAC system requires its own phone line, and the contractor must have a dedicated modem line as well. Moreover, the conventional system does not allow for easy customer modifications to the message profile. The conventional systems also do not allow the user to determine the failure rate of the equipment or to determine which pieces of equipment are best suited for a specific site.